The present invention relates to a method and a corresponding apparatus for detecting residual yarn remaining on spinning cop tubes, for use in automatic bobbin winding machines.
Modern spinning machines have a high output of spinning cops, and so more stringent demands are made of the processing capacity of the spinning machines downstream as well.
It is also necessary for the unwound tubes to be returned in adequate quantity to the spinning machine. To assure a high degree of automation, closed transport loops in the region of the spinning machine and optionally direct coupling of automatic bobbin winding machines to the spinning machines are therefore widely used.
In modern automated textile production facilities, the spinning cop tubes are thus subject to a circulatory process. The flow of material in such a closed spinning cop and tube transport system in the prior art, as known for instance from European Patent Disclosure EP 0 402 731 B1, is shown schematically in FIG. 6. Once the yarn has been made in a ring spinning machine, the resultant spinning cop is automatically delivered to the bobbin winding machine, where the cop is mounted on a cop carrier. Via conveyor belts, the spinning cop is transported from the mounting station to a cop preparation station 4, so that the end of the yarn can be separated thereby and made ready for being securely grasped later. The spinning cop then moves into a winding station 1, where the winding process is performed.
However, it can happen that the bobbin winder loses the beginning end of the yarn on the spinning cop in place, especially if the yarn breaks. After a few failed attempts at splicing, the spinning cop tube is treated as being presumably empty and is finally ejected from the spinning station 1. Thus, it is not assured that the ejected spinning cop tubes are in fact always empty. On the contrary, the ejected spinning cop tubes differ in terms of how much yarn remains on them and accordingly their reprocessing must be different.
To automate the winding process, it is therefore necessary to determine the status of the spinning cops shunted out of the winding station 1, so that individual residual yarn windings remaining on the cop tube or a possibly full or otherwise usable amount of residual yarn remaining on the spinning cop tube can be detected reliably. To that end, in the transport system shown in FIG. 6, an electromechanical tube monitor 2 is provided, which detects the amount of residual yarn remaining on the spinning cop tube.
The tube monitor 2 can be designed in the form of an electromechanical sensor (see for instance German Patent Application DE 41 10 626 A1), in which a metal comb sweeps laterally over the spinning cop tube. Depending on how far this comb can sweep over the tube, conclusions can be drawn as to the remaining quantity of yarn on the spinning cop tube. Spinning cops that have been completely unwound, i.e., empty tubes, are automatically transported back to the spinning machine to be refilled. Conversely, if a residual yarn remaining on the spinning cop tube has been detected by the tube monitor 2, then for instance with the aid of shunts the transport direction of the applicable spinning cop tube is diverted such that the spinning cop tube is delivered over a secondary route to a tube cleaning device 3. This tube cleaning device 3 has the task of removing the remaining yarn from the spinning cop tube. To that end, the yarn package is optionally cut open and then stripped off the spinning cop.
However, since it can also happen that the residual yarn remaining on the tube can still be reused and thus can be delivered to the spinning station 1 again, the tube monitor 2 also provides a statement as to whether the remaining yarn quantity detected on the spinning cop tube is sufficient to be reused. If so, then the spinning cop tube is not delivered to the tube cleaner 3 but rather is transported to the cop preparation unit 4, which in turn grasps the beginning of the yarn on the spinning cop and after placing this beginning end of the yarn at a predetermined point delivers the spinning cop to a winding station 1.
Instead of the design shown in FIG. 6, in which the tube monitor 2 serves as a multifunction sensor that can distinguish between empty tubes, tubes with a slight residual yarn, and tubes with a still usable residual yarn, it is also possible at the position of the tube monitor 2 to provide a first sensor, which detects merely whether a residual yarn is or is not present on the spinning cop tube. In that case, before a branching point toward the tube. cleaner 3, a further sensor is provided, which finally distinguishes whether or not the remaining residual yarn is sufficient for reuse and, by suitably controlling the transport route as a function of this decision, delivers the spinning cop tube either to the cop preparation station 4 or the tube cleaner 3.
As already explained above, in the bobbin winder shown in FIG. 6 an electromechanical spinning cop feeler in the form of a metal comb may be used as the tube monitor 2, but this has multiple disadvantages. For instance, in this design, the tube monitor 2 must be readjusted by hand for different types and sizes of spinning cop tubes. The metal comb can also wear down over time, and individual remaining yarns are not removed from the spinning cop tube but are instead merely pushed downward by the metal comb, so that these remaining yarns become tangled with the new yarn in an ensuing spinning process and thus can cause the ring spinning spindle to stop. It is also disadvantageous that the mechanical feeler elements of the sensor can damage the yarn, particularly fine yarns.
Japanese Patent Disclosure JP 63-107370 describes a similar mechanical sensor for detecting remaining yarns on spinning cop tubes. According to this reference, a rotatably supported mechanical arm is moved from top to bottom along the spinning cop tube and, depending on the degree to which the spinning cop tube is filled with yarn, the rotatably supported arm can be deflected to a variable extent. The deflection of the arm is detected with the aid of a suitable sensor, in order to draw conclusions as to any possible remaining yarn windings on the spinning cop tube.
In addition to the above-described detection of residual yarns on spinning cop tubes with the aid of mechanical sensors or feelers, devices are also known that detect remaining yarn or residual yarns on spinning cop tubes in contactless fashion.
To this end, German published examined Patent Application DE-AS 1 278 308 proposes irradiating the spinning cop tube with the aid of a light source such that the light reflected by the spinning cop tube may be detected with the aid of a photocell. The beam of light reflected from the spinning cop tube affects the photocell more or less, depending on whether a winding residue is or is not present on the spinning cop tube. During the scanning operation, a relative motion always occurs between the spinning cop tube and the photocell acting as a sensor, i.e., the spinning cop tube is moved horizontally past the photocell.
It is furthermore known from German Patent DE 40 08 795 C2, which defines the generic starting point for the present invention, to detect residual yarn remaining on a spinning cop tube by scanning the spinning cop tube with the aid of a relative motion between the spinning cop tube and a sensor, while the spinning cop tube is being transported in an upright disposition; the sensor is mounted on a stationary lifting divide, with the aid of which it is moved along the spinning cop tube with an approximately constant spacing from the surface of the tube. In particular, the sensor may be a photosensor, which evaluates light shone at a certain angle from the vertical onto the surface of the spinning cop tube and reflected back by the spinning cop tube, so as to detect residual yarns on the spinning cop tube.
Finally, Japanese Patent Disclosure JP 54-30943 also teaches contactless bobbin scanning. The apparatus disclosed in this reference is used to check sliver bobbins, in order to be able to check the exterior of the sliver bobbins for surface flaws, and so forth. The scanner proposed in this reference includes a light source, whose light is projected onto the sliver through a slit, designed and disposed to correspond to the comb line of the sliver bobbin. A television camera scans the sliver bobbin. In particular, the television camera scans the sliver bobbin line by line and on the basis of a comparison with reference values ascertains the quality of the sliver bobbin, so that bumps, winding gaps, and so forth in the sliver bobbin can be found. This apparatus is not, however, used to detect residual yarns or remaining yarn on spinning cop tubes.
It is accordingly an object of the present invention to create a method and a corresponding apparatus for detecting residual yarns on spinning cop tubes in which more certain and reliable detection of residual yarns is possible. With the aid of the present invention, it should also be possible not only to detect residual yarns but also to draw reliable conclusions about the degree to which the spinning cop is filled with residual yarn, so that if the spinning cop has reusable residual yarn it can be returned to a winding station, optionally after passing through a spinning cop preparation apparatus for finding the leading end of the yarn.
The above object is attained in accordance with the present invention by a method and apparatus of detecting residual yarn on spinning cop tubes, wherein a spinning cop tube is exposed to a suitable light source; the light reflected by the spinning cop tube is detected by a suitable means, e.g., via a camera or other picture-taking device, and two-dimensional picture signals of the spinning cop tube are generated thereby on the basis of the reflected light detected in order to generate a picture matrix comprising picture data in digital form; and the picture signals thusly generated are evaluated by means of performing an edge filtering of the digital picture data in order to segment image edges corresponding to brightness transitions in the picture matrix, from which the presence of residual yarn on the spinning cop tube can be assessed based on the edge filtering. The preferred, advantageous forms of embodiment of the present invention, described more fully hereinafter, contribute to the best possible scanning of the spinning cop tubes and the simplest possible, yet still reliable evaluation of the information obtained in the process.
Also in accordance with the present invention, residual yarns are detected in contactless fashion, yet digital picture signals are generated which can be subjected to digital image processing. In order to obtain object contours of the spinning cop tube to be examined from the digital picture data, an edge filter algorithm is employed, with the aid of which edges in the pictured image, i.e., transitions between brightness or gray values, can be emphasized or enhanced in the digital picture matrix. On the basis of the object contours thusly obtained, a reliable assessment of the yarn winding status of the applicable spinning cop tube is possible, so that in particular slight residual yarns on the spinning cop tube can be detected, and if greater residual yarn quantities are present, it can be assessed whether the package remainders thus detected can be reused.
The region of a spinning cop tube to be checked is as a rule the entire region which in a fully wound cop carries the yarn windings. However, it may also suffice to check only the lower third of the tube, which is where residual yarn is most likely to remain.
Scanning the spinning cop tube can be done in the present invention, particularly during transport of the spinning cop tube, in the form of a snapshot made by a full-frame camera. This camera may in particular be a CCD video camera, and a black and white picture suffices. To improve the picture utilization, or in other words to attain higher image resolution, optical distortion can be provided via a cylindrical optical element or concave mirror. Rotating the camera 90 degrees about its optical axis also contributes to higher image resolution. With the aid of a picture converter, the picture signal furnished by the video camera can be digitized and made available to a downstream evaluation computer, for instance in the form of a conventional personal computer. There, the picture is analyzed with a specially developed evaluation algorithm from which a reliable conclusion may be made about the yarn winding status of the specimen examined.
Instead of a CCD video camera, a digital still camera can also be used to scan the spinning cop tubes; in such a digital still camera, the digitization of the picture taken is done internally in the camera, so that later digitization using a picture converter is unnecessary.
A specimen is advantageously illuminated using a light source that projects diffused light. Such a light source can for instance comprise a plurality of arrays of ultra-bright light-emitting diodes (LEDs). These LED arrays are disposed such that the edges and contours of the spinning cop are enhanced or emphasized and no disturbing reflection occurs. The long service life, sturdiness and low power consumption of LEDs are advantages. By mixing the colors of the LEDs (red, green and yellow), the color spectrum can be widened. By using a diffuser, for instance in the form of a ground-glass plate or diffusing lens or screen, homogeneous illumination of the particular specimen can be achieved despite the intrinsically point-wise projection characteristic of LEDs. The disposition of the LEDs should advantageously be such that total reflection of the light from these LEDs to the applicable camera or other picture-taking device cannot occur. Instead of the use of different-colored LEDs, white LEDs that have recently become increasingly available on the market can also be used.
The digital image processing performed according to the present invention is based substantially on the extraction and analysis of the object structures of the applicable specimen, in particular the edges of the tube, the yarn layers, and the specific characteristics of the tube. To improve the contrast between the background, the spinning cop tube and the yarn windings, the digital picture matrix can be alternatingly squared, scaled back, and finally added back again to the original picture matrix. For edge filtering, Sobel""s filter algorithm can particularly be employed; the picture data thus processed are then binarized with the aid of a dynamic threshold value. For the sake of the most exact possible enhancement of the picture matrix, the object contours obtained by processing the picture data in this manner can subsequently be thinned with the aid of an erosion process with ensuing finding of the difference and, finally, the contour edges of the spinning cop tube being examined are extracted with the aid of a special edge tracing method, for instance by applying the Freeman chain code. The interpretation of the object contours extracted in this way is then done by assessment of their geometric shape or alternatively by a comparison with a reference picture of a comparison spinning cop tube.
In the picture taking method according to the present invention, it is not necessary for the applicable specimen to be stopped in front of the picture-taking device. That is, the detection of remaining yarn is advantageously done while the applicable spinning cop tube is moving past the picture-taking device.